Australian researchers Lee and colleagues reviewed the neuropsychological functioning during first episode depression.Neuropsychological deficits are considered to be part of depression and have implications for outcome. For example, cognitive impairments in MDD are associated with higher rates of relapse and recurrence (Fossati et al., 2002; Majer et al., 2004). Demographic and clinical factors are likely to obscure the interpretation of cognitive data( Eg: Premorbid intelligence and occupational attainment are positively associate with neuro psych performance. (Elgamal et al 2010).
literature after 1990 was reviewed, as this was the first time the current construct of “major depression” was in wide-use in the scientific literature .
Domains included were psychomotor speed, attention, working memory, verbal and visual learning and memory, attentional switching, verbal fluency and cognitive flexibility.
In total, 13 studies (15 samples) were included in the final analysis .
First-episode MDD patients performed significantly worse than healthy controls in psychomotor speed tasks (Hedges’ g = 0.48, p b 0.001) with moderate to high heterogeneity across studies.Patients had significantly worse attention (Hedges’ g = 0.36, p b 0.005).Verbal learning and memory performance was not significantly worse in patients (Hedges’ g = 0.13, p = 0.40). With regards to executive functioning, attentional switching was significantly worse in patients (Hedges’ g = 0.22, p = 0.05).Verbal fluency performance was significantly worse in patients (Hedges’ g = 0.59, p = 0.05) Cognitive flexibility was also significantly worse in patients (Hedges’ g = 0.53, p = 0.001)
There were small to medium effect sizes for six out of the eight domains investigated (psychomotor speed, attention, visual learning and memory, attentional switching, verbal fluency and cognitive flexibility)
Inpatient status significantly accounted for psychomotor speed and visual learning and memory performance, suggesting that these cognitive deficits may be linked to mood state . However, attentional or executive dysfunction was not affected by inpatient status, which is in keeping with previous research. i.e. these cognitive deficits may be important trait-markers for MDD, since they persist despite remission of depressive symptoms
Antidepressant use was also associated with better cognitive flexibility in this meta- analysis, consistent with previous findings .However, antidepressant use was associated with poorer verbal learning and memory functioning, which contradicts previous longitudinal findings demonstrating its effectiveness in reducing verbal memory deficits
Age and years of education appeared to explain some of the heterogeneity in cognitive outcome.
Limitations: Heterogeneity is likely to obscure the interpretation of the findings. All studies have small samples. Demographic and clinical character- istics of patient samples were insufficiently reported. No controlling done for potentially confounding effects of vascular risk factors and medication use
Clinical Practice: Attention should be given to cognitive deficits during depression. some defects may require specific interventions. Cognitive remediation (a range of interventions that target cognition through restorative and compensatory behavioural techniques) during an episode of depression is one such effort.
A meta-analysis of cognitive deficits in first-episode Major Depressive Disorder. Lee RS, Hermens DF, Porter MA, Redoblado-Hodge MA. J Affect Disord. 2012 Oct;140(2):113-24.